US 8144063 B2
Portable electronic devices are provided with wireless circuitry that includes antennas and antenna isolation elements. The antennas may include antennas that have multiple arms and that are configured to handle communications in multiple frequency bands. The antennas may also include one or more antennas that are configured to handle communications in a single frequency band. The antennas may be coupled to different radio-frequency transceivers. For example, there may be first, second, and third antennas and first and second transceivers. The first and third antennas may be coupled to the first transceiver and the second antenna may be coupled to the second transceiver. The antenna isolation elements may be interposed between the antennas and may serve to reduce radio-frequency interference between the antennas. There may be a first antenna isolation element between the first and second antennas and a second antenna isolation element between the second and third antennas.
1. Portable electronic device antenna structures in a portable electronic device, comprising:
first, second, and third resonating elements aligned along a common axis parallel to a ground plane and that are each connected to the ground plane, wherein the first and second resonating elements are fed using respective antenna feed terminals and form respective first and second antennas and wherein the third resonating element is not fed by any antenna feed terminals.
2. The portable electronic device antenna structures defined in
a first transmission line having a first positive conductor coupled to the antenna feed terminal of the first resonating element and a first ground conductor coupled to the ground plane; and
a second transmission line having a second positive conductor coupled to the antenna feed terminal of the second resonating element and a second ground conductor coupled to the ground plane.
3. The portable electronic device antenna structures defined in
4. The portable electronic device antenna structures defined in
5. The portable electronic device antenna structures defined in
6. The portable electronic device antenna structures defined in
7. The portable electronic device antenna structures defined in
8. The portable electronic device antenna structures defined in
9. The portable electronic device antenna structures defined in
10. The portable electronic device antenna structures defined in
11. The portable electronic device antenna structures defined in
12. A portable electronic device, comprising:
first, second, and third resonating elements that are parallel to a common axis and that are each connected to a common ground element, wherein the first and second resonating elements are fed using respective antenna feed terminals and form respective first and second antennas and wherein the third resonating element is not fed by any antenna feed terminals;
a first transmission line having a first positive conductor coupled to the antenna feed terminal of the first resonating element and a first ground conductor coupled to the common ground element; and
a second transmission line having a second positive conductor coupled to the antenna feed terminal of the second resonating element and a second ground conductor coupled to the common ground element.
13. The portable electronic device defined in
14. The portable electronic device defined in
15. The portable electronic device antenna structures defined in
16. The portable electronic device antenna structures defined in
17. The portable electronic device antenna structures defined in
18. The portable electronic device antenna structures defined in
19. The portable electronic device antenna structures defined in
This application is a continuation of patent application Ser. No. 11/969,684, filed Jan. 4, 2008, now U.S. Pat. No. 7,916,089 which is hereby incorporated by referenced herein in its entirety.
This invention relates generally to wireless communications circuitry, and more particularly, to wireless communications circuitry with antenna isolation for electronic devices such as portable electronic devices.
Handheld electronic devices and other portable electronic devices are becoming increasingly popular. Examples of handheld devices include handheld computers, cellular telephones, media players, and hybrid devices that include the functionality of multiple devices of this type. Popular portable electronic devices that are somewhat larger than traditional handheld electronic devices include laptop computers and tablet computers.
Due in part to their mobile nature, portable electronic devices are often provided with wireless communications capabilities. For example, handheld electronic devices may use long-range wireless communications to communicate with wireless base stations. Cellular telephones and other devices with cellular capabilities may communicate using cellular telephone bands at 850 MHz, 900 MHz, 1800 MHz, and 1900 MHz. Portable electronic devices may also use short-range wireless communications links. For example, portable electronic devices may communicate using the Wi-Fi® (IEEE 802.11) band at 2.4 GHz and the Bluetooth® band at 2.4 GHz. Communications are also possible in data service bands such as the 3G data communications band at 2170 MHz band (commonly referred to as UMTS or Universal Mobile Telecommunications System band).
To satisfy consumer demand for small form factor wireless devices, manufacturers are continually striving to reduce the size of components that are used in these devices. For example, manufacturers have made attempts to miniaturize the antennas used in handheld electronic devices.
A typical antenna may be fabricated by patterning a metal layer on a circuit board substrate or may be formed from a sheet of thin metal using a foil stamping process. Antennas such as planar inverted-F antennas (PIFAs) and antennas based on L-shaped resonating elements can be fabricated in this way. Antennas such as PIFA antennas and antennas with L-shaped resonating elements can be used in handheld devices.
Although modern portable electronic devices often use multiple antennas, it is challenging to produce successful antenna arrangements in which multiple antennas operate in close proximity to each other without experiencing undesirable interference.
It would therefore be desirable to be able to provide improved antenna structures for wireless electronic devices.
A portable electronic device such as a handheld electronic device is provided with wireless communications circuitry that includes antennas and antenna isolation elements. The antenna isolation elements may be interposed between respective antennas to reduce radio-frequency interference between the antennas and thereby improve antenna isolation.
With one suitable arrangement, there are at least three antennas in the wireless communications circuitry. The three antennas may each have a respective antenna resonating element. The antenna resonating elements may be formed from conductive structures such as traces on a flex circuit or stamped metal foil structures (as examples). Each antenna resonating element may have at least one antenna resonating element arm. The arms may be aligned along a common axis.
The antenna isolation elements may be formed from antenna isolation resonating elements such as L-shaped strips of conductor. The L-shaped conductive strips may have arms that are aligned with the common axis.
The antennas and the antenna isolation elements may share a common ground plane. With this type of configuration, a first antenna resonating element and the ground plane form a first antenna, a second antenna resonating element and the ground plane form a second antenna, a third antenna resonating element and a ground plane form a third antenna, a first antenna isolation resonating element and the ground plane form a first antenna isolation element, and a second antenna isolation resonating element and the ground plane form a second antenna isolation element.
If desired, some of the antennas and resonating elements may have multiple arms. For example, the first and third antenna resonating elements may have arms that are aligned with the common axis and arms that are perpendicular to the common axis.
The first and third antennas may be used to implement an antenna diversity scheme. With one suitable arrangement, a Wi-Fi transceiver that operates at 2.4 GHz and 5.1 GHz is coupled to the first and third antennas, whereas a Bluetooth transceiver that operates at 2.4 GHz is coupled to the second antenna. Antenna isolation elements that operate at 2.4 GHz may be placed between the first and second antennas and between the second and third antennas, thereby isolating the first antenna from the third antenna at 2.4 GHz and isolating the first and third antennas from the second antenna at 2.4 GHz.
Further features of the invention, its nature and various advantages will be more apparent from the accompanying drawings and the following detailed description of the preferred embodiments.
The present invention relates generally to wireless communications, and more particularly, to wireless electronic devices and antennas for wireless electronic devices.
The wireless electronic devices may be portable electronic devices such as laptop computers or small portable computers of the type that are sometimes referred to as ultraportables. Portable electronic devices may also be somewhat smaller devices. Examples of smaller portable electronic devices include wrist-watch devices, pendant devices, headphone and earpiece devices, and other wearable and miniature devices. With one suitable arrangement, the portable electronic devices are handheld electronic devices.
The wireless electronic devices may be, for example, cellular telephones, media players with wireless communications capabilities, handheld computers (also sometimes called personal digital assistants), remote controllers, global positioning system (GPS) devices, and handheld gaming devices. The wireless electronic devices may also be hybrid devices that combine the functionality of multiple conventional devices. Examples of hybrid portable electronic devices include a cellular telephone that includes media player functionality, a gaming device that includes a wireless communications capability, a cellular telephone that includes game and email functions, and a portable device that receives email, supports mobile telephone calls, has music player functionality and supports web browsing. These are merely illustrative examples.
An illustrative portable electronic device in accordance with an embodiment of the present invention is shown in
Device 10 may have housing 12. Antennas for handling wireless communications may be housed within housing 12 (as an example).
Housing 12, which is sometimes referred to as a case, may be formed of any suitable materials including, plastic, glass, ceramics, metal, or other suitable materials, or a combination of these materials. In some situations, housing 12 or portions of housing 12 may be formed from a dielectric or other low-conductivity material, so that the operation of conductive antenna elements that are located in proximity to housing 12 is not disrupted. Housing 12 or portions of housing 12 may also be formed from conductive materials such as metal. An illustrative housing material that may be used is anodized aluminum. Aluminum is relatively light in weight and, when anodized, has an attractive insulating and scratch-resistant surface. If desired, other metals can be used for the housing of device 10, such as stainless steel, magnesium, titanium, alloys of these metals and other metals, etc. In scenarios in which housing 12 is formed from metal elements, one or more of the metal elements may be used as part of the antennas in device 10. For example, metal portions of housing 12 may be shorted to an internal ground plane in device 10 to create a larger ground plane element for that device 10. To facilitate electrical contact between an anodized aluminum housing and other metal components in device 10, portions of the anodized surface layer of the anodized aluminum housing may be selectively removed during the manufacturing process (e.g., by laser etching).
Housing 12 may have a bezel 14. The bezel 14 may be formed from a conductive material and may serve to hold a display or other device with a planar surface in place on device 10. As shown in
Display 16 may be a liquid crystal diode (LCD) display, an organic light emitting diode (OLED) display, or any other suitable display. The outermost surface of display 16 may be formed from one or more plastic or glass layers. If desired, touch screen functionality may be integrated into display 16 or may be provided using a separate touch pad device. An advantage of integrating a touch screen into display 16 to make display 16 touch sensitive is that this type of arrangement can save space and reduce visual clutter.
Display screen 16 (e.g., a touch screen) is merely one example of an input-output device that may be used with electronic device 10. If desired, electronic device 10 may have other input-output devices. For example, electronic device 10 may have user input control devices such as button 19, and input-output components such as port 20 and one or more input-output jacks (e.g., for audio and/or video). Button 19 may be, for example, a menu button. Port 20 may contain a 30-pin data connector (as an example). Openings 24 and 22 may, if desired, form microphone and speaker ports. In the example of
A user of electronic device 10 may supply input commands using user input interface devices such as button 19 and touch screen 16. Suitable user input interface devices for electronic device 10 include buttons (e.g., alphanumeric keys, power on-off, power-on, power-off, and other specialized buttons, etc.), a touch pad, pointing stick, or other cursor control device, a microphone for supplying voice commands, or any other suitable interface for controlling device 10. Although shown schematically as being formed on the top face of electronic device 10 in the example of
Electronic device 10 may have ports such as port 20. Port 20, which may sometimes be referred to as a dock connector, 30-pin data port connector, input-output port, or bus connector, may be used as an input-output port (e.g., when connecting device 10 to a mating dock connected to a computer or other electronic device). Device 10 may also have audio and video jacks that allow device 10 to interface with external components. Typical ports include power jacks to recharge a battery within device 10 or to operate device 10 from a direct current (DC) power supply, data ports to exchange data with external components such as a personal computer or peripheral, audio-visual jacks to drive headphones, a monitor, or other external audio-video equipment, a subscriber identity module (SIM) card port to authorize cellular telephone service, a memory card slot, etc. The functions of some or all of these devices and the internal circuitry of electronic device 10 can be controlled using input interface devices such as touch screen display 16.
Components such as display 16 and other user input interface devices may cover most of the available surface area on the front face of device 10 (as shown in the example of
Examples of locations in which antenna structures may be located in device 10 include region 18 and region 21. These are merely illustrative examples. Any suitable portion of device 10 may be used to house antenna structures for device 10 if desired.
If desired, electronic device 10 may be a portable electronic device such as a laptop or other portable computer. For example, electronic device 10 may be an ultraportable computer, a tablet computer, or other suitable portable computing device. An illustrative portable electronic device 10 of this type is shown in
A schematic diagram of an embodiment of an illustrative portable electronic device is shown in
As shown in
Processing circuitry 36 may be used to control the operation of device 10. Processing circuitry 36 may be based on a processor such as a microprocessor and other suitable integrated circuits. With one suitable arrangement, processing circuitry 36 and storage 34 are used to run software on device 10, such as internet browsing applications, voice-over-internet-protocol (VOIP) telephone call applications, email applications, media playback applications, operating system functions, etc. Processing circuitry 36 and storage 34 may be used in implementing suitable communications protocols. Communications protocols that may be implemented using processing circuitry 36 and storage 34 include internet protocols, wireless local area network protocols (e.g., IEEE 802.11 protocols—sometimes referred to as Wi-Fi®), protocols for other short-range wireless communications links such as the Bluetooth® protocol, protocols for handling 3G data services such as UMTS, cellular telephone communications protocols, etc.
Input-output devices 38 may be used to allow data to be supplied to device 10 and to allow data to be provided from device 10 to external devices. Display screen 16, button 19, microphone port 24, speaker port 22, and dock connector port 20 are examples of input-output devices 38.
Input-output devices 38 can include user input-output devices 40 such as buttons, touch screens, joysticks, click wheels, scrolling wheels, touch pads, key pads, keyboards, microphones, cameras, etc. A user can control the operation of device 10 by supplying commands through user input devices 40. Display and audio devices 42 may include liquid-crystal display (LCD) screens or other screens, light-emitting diodes (LEDs), and other components that present visual information and status data. Display and audio devices 42 may also include audio equipment such as speakers and other devices for creating sound. Display and audio devices 42 may contain audio-video interface equipment such as jacks and other connectors for external headphones and monitors.
Wireless communications devices 44 may include communications circuitry such as radio-frequency (RF) transceiver circuitry formed from one or more integrated circuits, power amplifier circuitry, passive RF components, antennas, and other circuitry for handling RF wireless signals. Wireless signals can also be sent using light (e.g., using infrared communications).
Device 10 can communicate with external devices such as accessories 46 and computing equipment 48, as shown by paths 50. Paths 50 may include wired and wireless paths. Accessories 46 may include headphones (e.g., a wireless cellular headset or audio headphones) and audio-video equipment (e.g., wireless speakers, a game controller, or other equipment that receives and plays audio and video content), a peripheral such as a wireless printer or camera, etc.
Computing equipment 48 may be any suitable computer. With one suitable arrangement, computing equipment 48 is a computer that has an associated wireless access point (router) or an internal or external wireless card that establishes a wireless connection with device 10. The computer may be a server (e.g., an internet server), a local area network computer with or without internet access, a user's own personal computer, a peer device (e.g., another portable electronic device 10), or any other suitable computing equipment.
The antenna structures and wireless communications devices of device 10 may support communications over any suitable wireless communications bands. For example, wireless communications devices 44 may be used to cover communications frequency bands such as the cellular telephone bands at 850 MHz, 900 MHz, 1800 MHz, and 1900 MHz, data service bands such as the 3G data communications band at 2170 MHz band (commonly referred to as UMTS or Universal Mobile Telecommunications System), the Wi-Fi® (IEEE 802.11) bands at 2.4 GHz and 5.0 GHz (also sometimes referred to as wireless local area network or WLAN bands), the Bluetooth® band at 2.4 GHz, and the global positioning system (GPS) band at 1550 MHz. The 850 MHz band is sometimes referred to as the Global System for Mobile (GSM) communications band. The 900 MHz communications band is sometimes referred to as the Extended GSM (EGSM) band. The 1800 MHz band is sometimes referred to as the Digital Cellular System (DCS) band. The 1900 MHz band is sometimes referred to as the Personal Communications Service (PCS) band.
Device 10 can cover these communications bands and/or other suitable communications bands with proper configuration of the antenna structures in wireless communications circuitry 44.
With one suitable arrangement, which is sometimes described herein as an example, the wireless communications circuitry of device 10 may have at least two antennas that are used in a diversity arrangement to handle communications in a first communications band. Antenna diversity arrangements use multiple antennas in parallel to obtain improved immunity to proximity effects and improved throughput. The antennas may operate in any suitable frequency band. For example, the antennas may be used to handle local area network (LAN) communications in a communications band that is centered at 2.4 GHz (e.g., the 2.4 GHz IEEE 802.11 frequency band sometimes referred to as Wi-Fi®). If desired, antenna diversity arrangements may be implemented using more than two antennas (e.g., three or more antennas). For clarity, examples with two antennas are sometimes described herein as an example.
At least one additional antenna may be placed in close proximity to the diversity scheme antennas. The additional antenna may, for example, be placed in the vicinity of the other antennas to conserve space in electronic device 10. For example, the additional antenna may be placed between the other antennas. With one suitable arrangement, the antennas have resonating element structures with longitudinal axis that are all aligned.
The additional antenna may operate at the same frequency as the other antennas. For example, the additional antenna may operate at 2.4 GHz (e.g., to handle Bluetooth® communications). Because the antennas operate in the same communications band, care should be taken to avoid undesirable interference between the antennas.
The amount of isolation that is required between the antennas depends on the particular requirements of the system in which the antennas are being used. For example, the designers of portable electronic device 10 may require that the two diversity scheme antennas exhibit greater than 25 dB of isolation from each other and may require that the additional antenna exhibit greater than 15 dB of isolation relative to the other two antennas. These isolation criteria may be applied to antenna structures that exhibit a three-dimensional antenna efficiency of about 25-50%.
To achieve these levels of isolation, antenna isolation elements may be provided in the vicinity of the antennas. The structures that make up the antenna isolation elements may, for example, be interposed between the antenna resonating elements of the antennas. The antennas and the antenna isolation elements may share a common ground plane.
An illustrative antenna arrangement of this type is shown in
Transceiver 52 or other circuitry in device 10 may monitor the status of antennas 56 and 64 to implement an antenna diversity scheme. With this type of arrangement, transceiver 52 may use both antennas simultaneously or may opt to use primarily or exclusively antenna 56 or antenna 64 depending on which antenna has a higher associated signal strength or is less affected by proximity effects (e.g., from the close proximity of a user's hand or other part of a user's body), etc. Transceiver 52 may include coupling circuitry that routes radio-frequency signals to antenna 56 and/or antenna 64 from a transmitter in transceiver 52 during radio-frequency transmissions and that routes radio-frequency signals from antenna 56 and/or antenna 64 to a receiver in transceiver 52 during reception of radio-frequency signals. Transceiver 54 may include radio-frequency transmitter circuitry for transmitting radio-frequency signals and may include receiver circuitry for receiving radio-frequency signals.
During operation of device 10, it may be desirable to use transceiver 54 and transceiver 52 at the same time. The ability to operate transceivers 54 and 52 asynchronously may allow, for example, a user to use a Bluetooth headset to use device 10 to make a voice-over-internet-protocol (VOIP) telephone call. Transceiver 54 may be used to establish a wireless Bluetooth link with the Bluetooth headset. At the same time, transceiver 52 may be used to establish an IEEE 802.11(n) Wi-Fi link with a wireless access point connected to the Internet. Because both links may be used simultaneously, both links may carry data traffic without interruption.
The IEEE 802.11(n) protocol is an example of a protocol that may use antenna diversity to improve performance. This type of arrangement uses two antennas (e.g., antennas 56 and 64) to carry Wi-Fi traffic. In general, any suitable number of antennas such as antennas 56 and 64 may be used in an antenna diversity scheme. For example, there may be three or more antennas coupled to transceiver 52. The use of an arrangement with two diversity antennas is described herein as an example. Moreover, the Bluetooth link or other communications link that is established between transceiver 54 and antenna 60 is merely illustrative. There may be more than one antenna 60 and there may be more than one associated transceiver 54 that is coupled to that antenna if desired.
As shown in
Antenna 60 is generally located between antennas 56 and 64, as shown in
Because the printed circuit board and other conductive elements of ground plane 66 are electrically connected to form a common ground plane structure for antennas 56, 60, and 64, it may not be possible to create electrical gaps in ground plane 66 to help isolate antennas 56, 60, and 64 from each other. Particularly in situations such as these, it may be advantageous to use antenna isolation elements. As shown in
For example, with antenna isolation elements 58 and 62 in place, antennas 56 and 64 may exhibit greater than 25 dB of isolation from each other, whereas antenna 60 may exhibit greater than 15 dB of isolation relative to antennas 58 and 64. These isolation specifications may be achieved for antennas 56, 60, and 64 that exhibit three-dimensional antenna efficiencies of about 25-50% (as an example). Moreover, these isolation specification (or other suitable specifications) may be achieved when operating all antennas 56, 60, and 64 in the same frequency band (e.g., at 2.4 GHz or other suitable resonant frequency).
To enhance the capabilities of antennas 56, 60, and 64, some or all of antennas 56, 60, and 64 may operate in multiple communications bands. For example, antennas 56 and 64 may be configured to handle communications at both 2.4 Hz and 5.1 GHz (e.g., to handle additional Wi-Fi bands). In this type of configuration, radio-frequency transceiver (or an associated transceiver) may be used to convey signals at 5.1 GHz to and from antennas 56 and 64 over communications paths such as transmission lines 70 and 72 in addition to the 2.4 GHz signals that are being conveyed between the antennas and transceiver 52. Antenna 60 may be a single band antenna or may be a multiband antenna.
In a typical configuration, the resonating element structures of antennas 56, 60, and 64 and of antenna isolation elements 58 and 62 may have lateral dimensions on the order of a quarter of a wavelength at each frequency of interest (e.g., on the order of a couple of centimeters for 2.4 GHz communications). Antennas 56 and 64 may be separated by about 14 centimeters (as an example). Antenna 60 may be located midway between antennas 56 and 64. With one suitable arrangement, antennas 56, 60, and 64 and antenna isolation elements 58 and 62 are arranged in a line (i.e., along a common axis that is aligned with the longitudinal axis of each of the resonating elements in antennas 56, 60, and 64 and antenna isolation elements 58 and 62). Collinear arrangements such as these are illustrative. Other configurations (e.g., with different antenna resonating element sizes and/or different spacings and relative positions for the antennas) may be used if desired.
An illustrative configuration for an antenna such as antenna 56 or 64 is shown in
As shown in
Antenna resonating element 76, ground plane 66 and the other antenna structures in device 10 (including the resonating element structures associated with isolation elements 58 and 62) may be formed from any suitable conductive materials (e.g., copper, gold, metal alloys, other conductors, or combinations of such conductive materials). Such structures may be formed from stamped foils, from screen-printed structures, from conductive traces formed on flexible printed circuit substrates (so-called flex circuits) or using any other suitable arrangement.
In the example of
The horizontal portions of antenna resonating element 76 run parallel to ground plane 66. Antenna 74 of
If desired, some or all of the antennas and isolation elements can be located off of axis 92 (e.g., by a small offset amount such as by a few millimeters or by a relatively larger distance such as centimeter or more), but in general, such off-axis locations may not be highly favored because locating isolation elements 58 and 62 off of the longitudinal axis that runs through antennas 56, 60, and 64 will generally tend to reduce the effectiveness of isolation elements 58 and 62 in isolating the antennas from each other. Locating antennas 56, 60, and 64 at off-axis positions also tends to increase the overall footprint for the antennas, which makes it more difficult to fit the desired antenna structures into a device with a compact form factor.
The antennas in device 10 may be fed directly using feed terminals that are connected to portions of the antenna or indirectly through near-field coupling arrangements. In the illustrative example of
The antennas and isolation elements of device 10 may have dielectric support structures. An example of this type of arrangement is shown in
As shown in
Antenna feed terminals for antennas such as antenna 74 of
The bandwidth of an antenna such as the antenna of
Particularly in situations in which it is desirable to provide the higher-frequency band of a multi-band antenna with a maximized bandwidth (e.g., when handling the 5.1 GHz band of a 2.4 GHz/5.1 GHz dual-band Wi-Fi antenna), it may be advantageous to use an arrangement of the type shown in
A perspective view of an illustrative antenna configuration of the type that is shown schematically in
To ensure that isolation elements 58 and 62 provide satisfactory radio-frequency isolation for antennas 56, 60, and 64, the resonating element structures that make up antenna isolation elements 58 and 62 may be tuned to resonate at the frequency at which isolation is desired. For example, if antennas 56 and 64 resonate at 2.4 GHz and 5.1 GHz and antenna 60 resonates at 2.4 GHz, and if isolation is desired at 2.4 GHz, antenna isolation elements 58 and 62 may have L-shaped resonating elements of length L, where L is equal to a quarter of a wavelength at 2.4 GHz.
As shown in
In the example of
An alternative configuration for the antennas of device 10 is shown in
If desired, the antenna isolation elements may be located at positions that are offset somewhat from axis 92.
Isolation element 58 may be located so that it contacts ground plane 66 at point 118. In this type of situation, the resonant element of isolation element 58 will be positioned where indicated by solid line 120. As indicated by dashed line 122, in this configuration, the resonating element of antenna 56 is collinear with the resonating element of antenna isolation element 58. Because point 118 lies on line 122, there is no lateral offset between the location of resonating element 58 and the longitudinal axis of the antennas in device 10 (e.g., antenna 56 and the antennas that are not shown in
If desired, isolation element 58 may be located so that it contacts ground plane 66 at point 132. In this configuration, antenna isolation element 58 will be positioned where indicated by dashed line 134. Contact point 132 is offset from dashed line 122 by lateral offset distance 136. Provided that lateral offset 136 is not too large, antenna isolation element 58 may still provide sufficient isolation for the antennas of device 10. For example, a lateral offset of a fraction of a millimeter or a few millimeters may be acceptable for antennas that are a few centimeters in length.
Isolation element 58 may be provided with both a lateral and longitudinal offset with respect to antenna 56. This type of configuration is illustrated by dashed line 126. When the resonating element of antenna isolation element 58 is aligned with the position indicated by dashed line 126, the resonating element contacts ground plane 66 at point 124. As shown in
One isolation element, two isolation elements, or more than two isolation elements (e.g., in arrangements with four or more antennas) may be offset as shown in
The arms of the antenna isolation elements and/or antennas in device 10 may also be oriented at non-zero angles with respect to longitudinal axis 92 if desired. An example of this type of arrangement is shown in
Non-zero resonating element arm orientations of the type illustrated by the orientation of isolation element arm 138 of
If desired, one or more of the antenna isolation elements may be implemented using multiple resonating element structures. As shown in
The conductors of antenna isolation element 58 may have any suitable shape (e.g., L-shaped, multi-branched, shapes with bends, shapes with U-shaped and/or serpentine layouts, structures with combinations of these configurations, etc.). One of the antenna isolation elements may use multiple conductive structures, two of the antenna isolation elements may use multiple conductive structures, or (in arrangements using more than three antennas) three or more of the antenna isolation elements may use multiple conductive structures. The conductive structures in a given antenna isolation element may be substantially similar in shape or may have different shapes and sizes.
Antenna isolation elements 58 and 62 may be formed using multi-arm configurations. When the antenna isolation elements have multiple arms, the frequency response of the antenna isolation elements may be broadened to help enhance radio-frequency signal isolation effectiveness. An illustrative configuration in which antenna isolation element 58 is provided with multiple arms is shown in
Arm 146 may be longer than arm 148 (as an example). Arm 146 may be oriented so that it is parallel to longitudinal axis 92 of antennas such as antennas 56 and 60. Arm 148 may be oriented perpendicular to axis 92 and parallel to ground plane 66.
Additional suitable multi-arm configurations for the antenna isolation elements are shown in
In general, the antenna isolation elements may have one or more individual resonating element structures. The structures may have the same shapes and sizes or may have different shapes and sizes. The structures may have one arm (e.g., in an L-shaped conductive strip) or may have multiple arms. The structures may be aligned with the longitudinal axis of the antenna structures or may be oriented at a non-zero angle. Lateral and longitudinal offsets may be used in positioning the resonating element structures. Combinations of these arrangements may be used in forming antenna isolation elements.
Antennas such as antennas 56, 60, and 64 may also use these types of resonating element structures. For example, antenna 56 may be formed from two closely spaced resonating elements such as elements 156 and 160 of
The foregoing is merely illustrative of the principles of this invention and various modifications can be made by those skilled in the art without departing from the scope and spirit of the invention.